Inkjet printers are of various types including those on which one or more inkjet printheads, also known as pens, are mounted on a reciprocally moving so called scanning carriage, and others in which the pens may be mounted in a stationary position on a frame for so-called page wide printing. Scanning inkjet printers ordinarily have a pen servicing station located at some point on the path of travel of the pen carriage, typically to one side or the other of the print area, so that the scanning carriage and associated pens thereon can be moved to the service station for purging or “spitting”, priming, wiping, capping or otherwise servicing the pen orifices. The servicing station may include pen wipers, a source of pen servicing fluid and pen caps, some or all of which may be mounted in a stationary position or on a sled or other moveable support to bring the pens to be serviced and the service station into and out of operating proximity to each other for servicing. Inkjet printers with stationary printheads or pens which also may require periodic servicing may employ such a sled or moveable support to bring the service station to the stationary pens when servicing of the pen orifices is required.
Particularly in high speed printing using large format printer/plotters, the pen carriage and associated pens may be moved at speeds of 30–60 inches per second or even higher. Close control of the pen to paper or other media spacing (PPS) can improve print quality. Swath height error (SHE) is the variation (i.e., in the Y-direction in FIG. 1) in the swath of ink that the pen prints onto the media. Variation in the swath height directly impacts print quality and is responsible for swath boundary banding print defects. Single pass printing is especially sensitive to boundary banding because errors cannot be corrected with shingling or masking techniques as carriage speeds have increased. Dynamic swath height errors due to aerodynamic effects have therefore become an increasing problem, especially during single pass bi-directional printing. Single pass printing and rapid carriage speeds are therefore used for rapid printing. The leading and trailing pens on the carriage are most affected by this aerodynamic phenomenon.